Generally, for most of the known Back Electromotive Force (bemf) model-based Interior Permanent Magnet (IPM) position sensorless control schemes, the rotor position is estimated from the stator voltage and stator current relationship.
Due to the rotor saliency item of an IPM machine, the voltage equation-based bemf model has to be simplified by ignoring some dynamic transition related items. The position accuracy is thus greatly deteriorated in dynamic load transition and dynamic speed transition.
Another common disadvantage of the voltage equation based bemf model methods is that the position accuracy is sensitive to the generator inductance variation, the generator stator resistance variation, and the rotor flux magnitude variation. In practical operation, the generator inductance variation is significant due to magnetic circuit saturation. The generator stator resistance and rotor flux magnitude variation may also be significant due to generator operation temperature change.